Eager Request Body Buffering for Postponed Logging State

[kasmarian]

Description

Implement eager buffering by immediately buffering the request body when withBody() is called, before the stream closes. This ensures the body is cached and available to both:

• The downstream controller (via wrapped/buffered streams)
• The Logbook sink (for logging)

Motivation and Context

#2194

When using postponed logging strategies like body-only-if-status-at-least, request bodies were not reaching the controller. The issue was that:

• Logbook deferred body buffering until later in the request lifecycle
• By that time, the servlet container had already closed the input stream
• The controller received an empty request body

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All commits are signed

[ChristianLohmann]

👍

[lukasniemeier-zalando]

Warning:  Rule violated for class org.zalando.logbook.servlet.RemoteRequest.Offering: lines covered ratio is 0.9, but expected minimum is 1.0

[kasmarian]

@lukasniemeier-zalando fixed the build, but had to re-do the changes. Please have another look

[kasmarian]

@ChristianLohmann sorry, didn't ping you in the previous message, but since the changeset that you've approved is changed significantly, now, please have another look